442
JAMES E. DEACON AND W. L. MINCKLEY
port of fishes by flood or by movements of the fish up- or downstream,
such uniformity could scarcely persist. In one instance, however, when an
entire indigenous morphotype was destroyed by chemical eradication, reinvasion by a dowstream population was evidenced by changes in the morphology easily detectable by character analysis. Many such examples of
indicated stability are available in desert fishes, despite variations of environment that would seem directly opposed to such a phenomenon on
a long-term basis.
4. Broader Distributional Relations
Distributional patterns of fishes that range widely often appear to correlate with climate, chemical factors, relief, or a combination of these and
other environmental parameters (Hubbs, 1957b). This often involves species interactions at the margins of their ranges, such as in the speckled
and longfin daces in Arizona (Fig. 8). Boundaries, as discussed above,
may move up- and downstream with changes in runoff. Isolated populations may be severely limited in range, such as the cold-water trouts on.
desert mountains surrounded by hot or dry lower rivers which are totally
inhospitable to them (Miller, 1950a, 1971; Needham and Gard, 1964).
It is perhaps noteworthy that such trout now are as (or more) effectively
isolated as are pupfish in a spring; in actuality they are desert fishes too,
and as such serve to illustrate one of the difficulties involved in our selection of species to discuss here.
Excluding local isolates and some fishes so highly specialized, such as
Gila cypha, or thermal endemics such as Moapa, Crenichthys, and others,
as to be restricted to the biotope in which they presumably evolved, more
subtle patterns relative to environment are discernible. Pupfishes exploit
their remarkable tenacity for life by successfully occupying places unavailable to other fish species because of environmental extremes. With a
few exceptions, they never become abundant except in places too severe
for, or isolated from, a substantial, competing or predatory fish fauna.
This results in an apparently discontinuous distribution, even in integrated
river basins. The Pecos River of south-central United States flows through
an area of salt domes and strata from which solution occurs, and
salinities may approach that of seawater. Cyprinodontoids, some with
affinities to Atlantic and Gulf of Mexico coastal forms, dominate the local
fauna (Koster, 1957; Hubbs and Miller, 1965). Aquatic crustaceans
of similar affinity have also been found (Cole and Bousfield, 1970). In
the dilute headwaters of the Pecos, and in the Rio Grande above and below
the mouth of the Pecos, these fishes are rare, absent, or restricted to creek
mouths, backwaters, or other protected habitats. The Plains killifish seems
JAMES E. DEACON AND W. L. MINCKLEY
port of fishes by flood or by movements of the fish up- or downstream,
such uniformity could scarcely persist. In one instance, however, when an
entire indigenous morphotype was destroyed by chemical eradication, reinvasion by a dowstream population was evidenced by changes in the morphology easily detectable by character analysis. Many such examples of
indicated stability are available in desert fishes, despite variations of environment that would seem directly opposed to such a phenomenon on
a long-term basis.
4. Broader Distributional Relations
Distributional patterns of fishes that range widely often appear to correlate with climate, chemical factors, relief, or a combination of these and
other environmental parameters (Hubbs, 1957b). This often involves species interactions at the margins of their ranges, such as in the speckled
and longfin daces in Arizona (Fig. 8). Boundaries, as discussed above,
may move up- and downstream with changes in runoff. Isolated populations may be severely limited in range, such as the cold-water trouts on.
desert mountains surrounded by hot or dry lower rivers which are totally
inhospitable to them (Miller, 1950a, 1971; Needham and Gard, 1964).
It is perhaps noteworthy that such trout now are as (or more) effectively
isolated as are pupfish in a spring; in actuality they are desert fishes too,
and as such serve to illustrate one of the difficulties involved in our selection of species to discuss here.
Excluding local isolates and some fishes so highly specialized, such as
Gila cypha, or thermal endemics such as Moapa, Crenichthys, and others,
as to be restricted to the biotope in which they presumably evolved, more
subtle patterns relative to environment are discernible. Pupfishes exploit
their remarkable tenacity for life by successfully occupying places unavailable to other fish species because of environmental extremes. With a
few exceptions, they never become abundant except in places too severe
for, or isolated from, a substantial, competing or predatory fish fauna.
This results in an apparently discontinuous distribution, even in integrated
river basins. The Pecos River of south-central United States flows through
an area of salt domes and strata from which solution occurs, and
salinities may approach that of seawater. Cyprinodontoids, some with
affinities to Atlantic and Gulf of Mexico coastal forms, dominate the local
fauna (Koster, 1957; Hubbs and Miller, 1965). Aquatic crustaceans
of similar affinity have also been found (Cole and Bousfield, 1970). In
the dilute headwaters of the Pecos, and in the Rio Grande above and below
the mouth of the Pecos, these fishes are rare, absent, or restricted to creek
mouths, backwaters, or other protected habitats. The Plains killifish seems